1. Technical Field
The present invention relates to a manufacturing process of a liquid crystal display (LCD) device and an LCD device, and particularly relates to a manufacturing process including a step for sealing a liquid crystal layer with a sealant and a structure of a seal portion thereof.
2. Background Art
In recent years, an LCD device is widely used as a high-resolution display device. This LCD device includes two substrates. The one has switching elements such as thin film transistors (TFTs) (hereinafter, referred to as a TFT substrate) and the other has a color filter and a black matrix (hereinafter, referred to as a color filter substrate). In this LCD device, a liquid crystal material is sandwiched between the TFT substrate and the color filter substrate. These substrates are adhered by using a sealant on a periphery thereof, and a liquid crystal layer is sealed.
In a general LCD device, the sealant adheres to an inorganic protective insulating film extending to the periphery of the TFT substrate. In recent years, in order to improve an aperture ratio of a TFT substrate, an LCD device is put to practical use in which an organic interlayer insulating film is formed on an inorganic protective insulating film However, an adhesive force between an organic interlayer insulating film and a sealant decreases compared with one between an inorganic protective insulating film and a sealant. Therefore the sealant is designed to be arranged on the inorganic protective insulating film by adding a process of removing the organic interlayer insulating film on the seal portion of the TFT substrate. In this way, an improvement of adhesiveness is achieved.
An example of an LCD device having an organic interlayer insulating film is disclosed in Japanese Patent Application Laid-Open No. 2003-167258. The LCD device described in this gazette is shown in FIG. 11. FIG. 11A is a cross sectional view of an outer peripheral part thereof, and FIG. 11B is a cross sectional view of a pixel part. As shown in FIG. 11B, the TFT structure of this LCD device is a structure called a top gate type or a planar type. In the top gate type (the planer type) TFT structure, a polysilicon semiconductor layer 32, a gate insulating film 33, and a gate wiring 34 are formed in this order on a glass substrate 31. An inorganic protective insulating film 35 and an organic interlayer insulating film 36 are formed in this order on an upper surface of the gate wiring 34. Accordingly, by removing only two layers of the organic interlayer insulating film 36 and the inorganic protective insulating film 35 using an etching step, a contact hole can be formed. At that time, in a seal portion in which a sealant 37 is formed, since the layer structure is identical with that of the pixel part, the organic interlayer insulating film 36 and the inorganic protective insulating film 35 in the seal portion are also removed similarly. However, an inorganic interlayer insulating film 38 formed thereunder remains without being removed. Accordingly, the gate wiring 34 formed under the inorganic interlayer insulating film 38 can not be exposed in the seal portion during a contact hole formation process.